JP3673981B2 - X-ray diffraction quantitative device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray diffraction quantification apparatus that performs correction based on a change in diffraction X-ray intensity of a basal standard plate arranged behind a sample and obtains the weight of a specific substance contained in the sample.
[0002]
[Prior art]
For a sample containing a specified substance and other unspecified substances, there are cases where it is desired to know the weight and content of the specified substance with respect to the entire sample. For example, in a work site where there are many types of dust, if a harmful substance is included in the dust, the content of the harmful substance must be known and suppressed to a certain level or less.
[0003]
It has been conventionally known that the weight of a specific substance can be detected by measuring the diffracted X-ray intensity of the specific substance. Therefore, in principle, when a specific substance is contained in a sample, if the entire sample is irradiated with X-rays and the intensity of diffracted X-rays from the specific substance is measured, It is thought that the weight of the specific substance contained can be known.
[0004]
However, in practice, the sample contains non-specific substances in addition to the specific substance, and if the content of the specific substance changes, the amount of the non-specific substance correspondingly changes accordingly. When measuring the intensity of diffracted X-rays from a specific substance inside it, the measured diffracted X-ray intensity is affected by the X-ray absorption rate of the sample and does not accurately reflect the weight of the specific substance. . Accordingly, the specific substance contained in the sample cannot be accurately quantified as it is.
[0005]
In view of such problems, the effect of X-ray absorption by the sample is corrected, and the content of the specific substance can be accurately measured based on the X-ray diffraction measurement regardless of the content of the specific substance. As an X-ray diffraction determination method, an X-ray diffraction determination method using a basal standard absorption correction method is conventionally known. This basic standard absorption correction method can be simply described as the amount of change in the diffracted X-ray intensity of the base standard plate placed behind the sample with respect to the traveling direction of the incident X-ray, that is, the amount of change in the absorption coefficient of the sample. Based on this, the diffraction X-ray intensity from the specific substance in the sample is corrected, and the weight of the specific substance is determined based on the corrected diffraction X-ray intensity.
[0006]
In the X-ray diffraction quantification method based on this basal standard absorption correction method, it is necessary to actually measure the X-ray absorption rate of the sample. In the actual measurement, a filter with no sample attached is adhered to the basal standard plate. It is necessary to measure both the diffracted X-ray intensity of the base standard plate and the diffracted X-ray intensity of the base standard plate in a state where the filter to which the sample is adhered is adhered to the base standard plate. Conventionally, when performing these measurements, for example, as shown in FIG. 7, a filter 51 with a sample attached thereto or a filter 52 without a sample attached thereto is attached to a base standard plate 54 with a transparent tape 53 or the like. Then, the X-ray R1 is applied to each of the filter 51 with sample and the filter 52 without sample, and the diffracted X-ray R2 generated at that time is detected by the X-ray counter 56.
[0007]
[Problems to be solved by the invention]
However, in the conventional X-ray diffraction quantitative method, the entire basal standard plate 54 is formed of a basal standard substance, for example, Zn (zinc). Therefore, when the irradiation region of incident X-rays is set wider than the sample collection part of the filters 51 and 52 as indicated by the symbol A, there is a problem that a correct X-ray absorption rate cannot be measured. The reason for this is that although the X-ray counter 56 deviates from the filters 51 and 52, the diffraction X-ray information from only the region where the sample on the filters 51 and 52 is originally desired is desired. This is because the line information is also taken in.
[0008]
The present invention has been made in view of the above-mentioned problems in the conventional X-ray diffraction quantification method, and is reliable even without applying strict regulations on the irradiation region of incident X-rays in the X-ray diffraction quantification method. The purpose is to enable highly accurate measurement.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the X-ray diffraction quantification apparatus according to the present invention adds a correction based on a change in the diffracted X-ray intensity of a basal standard plate arranged behind the sample, and specifies the specific contained in the sample. Yes in X-ray diffraction apparatus for determining for determining the weight of material, a sample holder for holding the sample, and a small base standard plate area than the sample holder and a sample plate for supporting the sample holder The base standard plate is embedded in the sample plate, and the sample plate has X-ray diffraction characteristics different from the base standard plate .
[0010]
According to this X-ray diffraction quantification apparatus, the basal standard plate is always hidden under the sample holder with respect to the incident X-ray, so that the X-ray absorption is always accurate regardless of the irradiation width of the incident X-ray. The rate can be measured, and therefore, a reliable weight measurement can be performed on the specific substance contained in the sample.
[0011]
In a normal X-ray diffractometer, a sample is mounted on a goniometer, and the incident angle of incident X-rays with respect to the sample is measured based on the angle measuring function of the goniometer. In this X-ray diffractometer, a sample is generally mounted on the goniometer by supporting a sample holder with a sample plate provided in the goniometer. When such a sample plate is used, the sample plate can be formed of a material having X-ray diffraction characteristics different from that of the base standard plate, and the base standard plate can be embedded in the sample plate. If the base standard plate is made of, for example, Zn, the sample plate surrounding it can be made of, for example, Al (aluminum).
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of an X-ray diffraction quantitative apparatus according to the present invention. This X-ray diffraction quantification apparatus is used, for example, for measuring the content of specific harmful substances present in dust contained in the atmosphere. This X-ray diffraction quantitative apparatus has an X-ray focal point F that generates X-rays, a goniometer 1, and an X-ray counter 2. The X-ray focal point F includes, for example, a filament that emits electrons and a target that generates X-rays when the emitted electrons collide. Further, in the vicinity of the X-ray focal point F, a divergence regulation slit 3 for regulating the divergence angle of the X-ray is provided. The X-ray counter 2 can be configured using, for example, a scintillation counter (SC).
[0013]
The goniometer 1 has a θ rotation table 4 and a 2θ rotation table 6 coaxial with the θ rotation table 4, and the X-ray counter 2 is fixed to a detector arm 7 extending from the 2θ rotation table 6. Inside the goniometer 1, a θ rotation drive mechanism (not shown) for rotating the θ rotation table 4 around the sample axis Xs, so-called θ rotation, and the 2θ rotation table 6 about the sample axis Xs, so-called 2θ rotation A 2θ rotation drive mechanism (not shown) is provided. The 2θ rotation has the same rotation direction and the angular velocity is set to twice that of the θ rotation.
[0014]
The θ turntable 4 is provided with a leaf spring 8 or other holding mechanism. In the case of this embodiment, a rectangular sample plate 9 is inserted into the plate spring 8, and the sample plate 9 is fixed and held at a predetermined position by the spring force of the plate spring 8. A base standard plate 11 is embedded in a circular shape in a portion of the sample plate 9 irradiated with X-rays from the X-ray focal point F. As shown in FIG. 3, the base standard plate 11 and the sample plate 9 are set so that their surfaces are a uniform plane. In this embodiment, the base standard plate 11 is made of Zn, and the sample plate 9 is made of a material having a unique X-ray diffraction angle different from that of the base standard plate 11, for example, Al.
[0015]
On the base standard plate 11 embedded in the sample plate 9, as shown in FIG. 2, a sample holding filter 12, that is, a sample holding body holding dust in the air as a measurement target is attached. It is fixed by transparent tape or other fixing means. The sample holding filter 12 is formed of, for example, a glass fiber. In the present embodiment, the sample holding filter 12 is formed in a circular shape, and the area of the base standard plate 11 is set to be smaller than the area of the dust collecting portion 13 of the sample holding filter 12. That is, the dust on the filter 12 is mounted on the base standard plate 11 with the base standard plate 11 completely covered.
[0016]
Hereinafter, the X-ray diffraction quantitative measurement performed using the apparatus of the present embodiment will be described with reference to the process chart shown in FIG. First, the weight Wf of the single sample holding filter 12 is measured (step S1). Next, the sample holding filter 12 is attached to the base standard plate 11, and the diffracted X-ray intensity Izn0 of the base standard plate 11 is measured in this state (step S2). At this time, the incident angle θzn of the X-ray with respect to the base standard plate 11 is measured by the goniometer 1 in FIG. 1 to a value half the X-ray diffraction angle (2θ) specific to Zn which is the material of the base standard plate 11. Is done.
[0017]
Next, the sample holding filter 12 is once removed from the base standard plate 11, and the air to be measured is sucked toward the filter 12 to attach dust G to the filter 12 (step S3). . Thereafter, the weight Wm of the filter 12 to which the dust G is adhered is measured (step S4). Thereafter, the filter 12 to which the dust G is attached is again attached to the base standard plate 11, and in this state, the diffraction X-ray intensity Im of the specific substance contained in the dust G is measured (step S5). Also at this time, in FIG. 1, the X-ray incident angle specific to the specific substance is accurately measured by the goniometer 1.
[0018]
Thereafter, the X-ray incident angle is changed to a diffraction angle unique to the base standard plate 11 and measurement is performed, and the diffraction X-ray intensity Izn of the base standard plate 11 with the dust G attached is measured (step S6). Thereafter, in step S7, the following calculation is performed based on the above various measured values. That is,
It = K ・ Im
Based on the above formula, the diffraction X-ray intensity It of the specific substance after absorption correction is obtained.
In addition,
Im: diffracted X-ray intensity K of the specific substance actually measured K: correction coefficient.
[0019]
Further, the correction coefficient K is given by the following equation: K = −R · ln (ΔRi) / {1− (ΔRi) ^R }
Sought by.
However,
R = sin θzn / sin θm
θzn: X-ray diffraction angle θm of the base standard plate 11: X-ray diffraction angle ΔRi of the specific substance (actual measurement value of X-ray transmittance by dust as sample) = Izn / Izn0
It is.
[0020]
When the diffraction X-ray intensity It of the specific object after absorption correction is obtained as described above, the content m of the specific substance is obtained using a calibration curve L as shown in FIG. 5, for example. The calibration curve L is prepared based on data obtained by preparing a plurality of different known amounts of specific substances in advance and repeatedly executing the processing shown in FIG. .
[0021]
As described above, when the content m of the specific substance is obtained, the content Q (%) of the specific substance is expressed by the following formula Q = (m / W) × 100
Ask for. However,
W (amount of collected dust) = Wm -Wf
It is.
[0022]
In the present embodiment, as shown in FIG. 6, since the area of the base standard plate 11 is made smaller than the area of the dust collecting part 13 of the sample holding filter 12, the base standard plate 11 is completely hidden under the dust. . Accordingly, even when the X-ray irradiation area A is wide and projects outside the filter 12, the base standard plate 11 does not exist in the projecting portion, and therefore it is possible to prevent unnecessary diffraction X-rays from being generated. As a result, the X-ray transmittance ΔRi of the dust can always be accurately measured regardless of the X-ray irradiation width, and a highly reliable quantitative result can be obtained.
[0023]
The present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the embodiments, and various modifications can be made within the scope of the invention described in the claims.
For example, what can be quantified using the X-ray diffraction quantification apparatus of the present invention is not limited to specific harmful substances in dust, but can be applied to quantification work of all kinds of substances. Further, the sample holder for holding a sample such as dust is not limited to the shape and material of the filter 12 shown in FIG. 2, and can be any shape and material corresponding to the measurement site. In addition, the base standard plate and the sample plate surrounding the base standard plate can be formed using any material as long as the diffraction angles are different.
[0024]
【The invention's effect】
According to the X-ray diffraction quantification apparatus of the present invention , the basal standard plate is always hidden under the sample holder with respect to the incident X-ray, so that it is always accurate regardless of the irradiation width of the incident X-ray. X-ray absorption can be measured, and therefore, a reliable weight measurement can be performed on a specific substance contained in a sample.
[0025]
Moreover, according to the X-ray diffraction quantification apparatus according to the present invention, the present invention can be applied to a sample plate that is ordinarily widely used.
[0026]
In the X-ray diffraction quantitative apparatus according to the present invention , if the sample plate is made of aluminum and the base standard plate is made of zinc , good quantitative results can be obtained without using special materials as the base standard plate and the sample plate. be able to.
[0027]
[Brief description of the drawings]
FIG. 1 is a perspective view showing a main part of an embodiment of an X-ray diffraction quantitative apparatus according to the present invention.
FIG. 2 is a perspective view showing an embodiment of each of a sample holder, a base standard plate, and a sample plate.
3 is a cross-sectional view of the structure shown in FIG.
FIG. 4 is a process diagram showing a process procedure of X-ray diffraction quantitative measurement performed using the apparatus shown in FIG. 1;
5 is a graph showing an example of a calibration curve used in the measurement of FIG.
FIG. 6 is a plan view showing a relative positional relationship between a sample holder, a base standard plate, and an X-ray irradiation region.
FIG. 7 is a plan view schematically showing an example of a conventional X-ray diffraction quantitative apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Goniometer 2 X-ray counter 3 Divergence control slit 4 (theta) turntable 6 2theta turntable 7 Detector arm 8 Leaf spring 9 Sample plate 11 Base standard plate 12 Sample holding filter (sample holding body)
13 Filter dust collection part A X-ray irradiation area F X-ray focal point G Dust (sample)

Claims (2)

In the X-ray diffraction quantification apparatus for correcting the weight based on the change in the diffracted X-ray intensity of the basal standard plate arranged behind the sample and obtaining the weight of the specific substance contained in the sample,
A sample holder for holding the sample,
A basal standard plate having a smaller area than the sample holder,
A sample plate for supporting the sample holder,
The base standard plate is embedded in the sample plate,
The X-ray diffraction quantification apparatus, wherein the sample plate has X-ray diffraction characteristics different from those of the basal standard plate . In X-ray diffraction quantification apparatus according to claim 1, the sample plate is made of aluminum, X-ray diffraction apparatus for determining, characterized in that the formation of the base standard plate with zinc.

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